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Porsche 911 RSR Turbo – On track in 500bhp Le Mans monster

Porsche 911 RSR Turbo – On track in 500bhp Le Mans monster Classic and Performance Car

This Porsche 911 was the first turbocharged car to compete at Le Mans – so successfully that every Le Mans Porsche since has been force-fed. John Barker discovers a racing legend 


What a crazy-looking car. I’ve seen plenty of pictures of the Carrera RSR Turbo 2.1, but to walk out into the pitlane at Rockingham Raceway and find it parked there is like going into your living room and finding David Bowie sitting on your sofa. I can’t help but laugh out loud. The confidence, the vision, the audacity that Porsche had to build something this off-the-wall is breathtaking even today – what must its rivals have thought when it was wheeled out into the pitlane at Le Mans in 1974? 
 
The RSR Turbo is the extraordinary answer to an extraordinary question, that question being: what do we need to do to make a 911 RSR competitive if we stuff a 500bhp, turbocharged flat-six in the back? According to Norbert Singer, then just a few years into his career at Porsche, part of the answer was to fit 15in-wide rear slicks and the most enormous rear wing. FIA Group 5 was a silhouette class but, because race cars exist to sell road cars, the RSR Turbo had to look like a 911, so that huge wing was painted black in an attempt to make it less obvious. 
 
Porsche built just four of these 2.1 Turbos, all of which were given ‘R’ numbers and, clearly not being superstitious, this is R13. It proved the most successful of the three that saw competitive action (the fourth was a development car), finishing second overall at Le Mans in 1974. This was an incredible achievement when you consider that it was the first turbocharged car ever to compete in the 24-hour classic and was up against a phalanx of proven, low-slung, open-cockpit sports prototypes: Matras, Lolas, Gulf Mirages, Ligiers, Chevrons and a couple of Porsche 908s. 

Porsche 911 RSR Turbo

In comparison with them, the RSR Turbo looked like a Funny Car dragster, its low, obviously 911 front end rising and then distending into caricature. Its rear side windows were replaced with panels with NACA ducts and the buttresses and rear wing extended its overall length.
 
And what a view from the rear. It’s the hefty turbo hanging in the wide cut-out that draws the eye. Then you notice the original 911 tail-lights either side of it. Flanked by the cartoonishly wide rear ’arches, the lights look so far inboard that you wonder if the original shell has been narrowed, but no: it’s just that the inside edges of the road-roller-like rear tyres sit outboard of where a standard 911’s wheelarches would finish…  
 
It was pretty effective, too. The fastest of the sports prototypes qualified with lap times in the 3min 36sec range; the RSR Turbo was only about 16 seconds a lap slower than that but about 20 seconds faster than the 3.0 RSRs. It proved remarkably reliable and despite issues late on, could even have won outright. 
 
It looks like the sort of car that would need a mechanic with a portable starter motor to poke around the back to churn the engine and get it going. It doesn’t. ‘It’s a Porsche: it starts first time on the key,’ grins Simon Harper, who works for the current owner.
 
Our driver, the hugely experienced Joe Twyman, straps in, turns the disarmingly standard-looking key that’s poking out of the scrappy dashboard, and the flat-six fires up with a chug of dark smoke from the single tailpipe. It idles with a sound that’s got some blare to it but is surprisingly moderate given that the header pipes feed into the hulking great KKK turbocharger and then go straight to atmosphere.
 
Porsche 911 RSR Turbo

As it pulls away, the note is hard-edged though not coarse, the typically lazy, confident flat-six beat staying high for a few yards, testimony to a long first gear, and then it’s out of sight. We all stand and listen, tracking its progress aurally. It’s a bit hesitant at first, reluctant to pull revs, but it hasn’t been used in anger for many years and Joe is treating it respectfully. 
 
As it comes past the pits on the banking, still far from full-throttle, the flat-six drawl ricochets off the stands. For me, this is the sound of Le Mans: the noise I went to sleep with and hours later woke up to. By the third lap, the RSR’s engine is coming on song and the sound has gained an extra element: a high-pitched whine reminiscent of a jet engine. ‘That’s the turbo,’ smiles Simon.
 
The quoted output of the 2142cc flat-six is 450-500bhp at 7600rpm, an output that would be impressive still today. That capacity was chosen so that, with the FIA turbo equivalency factor of 1.4:1, the car would still be under the 3.0-litre limit for the prototype Group 5 class. Practically, the capacity was achieved by reducing both the bore and the stroke of the naturally aspirated 3.0-litre RSR engine, while to keep weight down its crankcase was cast in magnesium alloy. 
 
Porsche had two seasons of experience of using turbochargers in competition with the 917, and had won the 1973 CanAm championship convincingly with the incredible 917/30, the 1100bhp monster driven by Mark Donohue. The RSR Turbo’s KKK ‘33’ turbocharger boosts to 1.4bar (20psi) and the engine is fed by mechanical fuel injection. Unlike the stock engine, the cooling fan sits on top of the engine (as in the flat-12s) rather than facing the rear because, although turning the drive 90º consumes more energy, this is more than offset by the fan cooling the air-cooled engine block better, allowing it to make more power. 
 
Back in the pits, the turbocharger is still spooling down a good few seconds after the engine has been cut. The RSR is now exuding that rich-running, part-burnt-hydrocarbons aroma that old racers so often have. 

Porsche 911 RSR Turbo
 
It’s clear that R13 has never been restored. In fact, I could quite believe that, since its last competitive outing 40 years ago, it has only been washed to get the bugs off. The patina is glorious. There are nicks and scratches, stone-peck on the wing tops and missing paint on an ’arch where another car’s tyre has rubbed. The Martini stripes that flow sensually around the RSR’s curves were clearly applied by hand and even the sponsors’ decals are signwritten; you can see the brush-strokes in the almost transluscent ‘MARTINI PORSCHE’ script, as if two coats of paint would have been unnecessarily heavy.
 
I’m only half-joking. The more you look, the more you discover a fanatical approach to weight-saving. The bonnet shield is a transfer rather than an enamel badge and the doorhandles look like the standard metal ones painted black, but are in fact moulded from lightweight black plastic.
 
Take hold, push the button and swing the door open. It feels as light as a crisp packet, and probably offers about as much side-impact protection because there are neither door-bars nor cross-bracing for the aluminium rollcage. Yep, aluminium. 
 
Every single possible gram has been shaved off, like it’s an aircraft. And like an aircraft, it was designed to fly, not crash. Different times.
 
There’s not much of the original 911 steel bodyshell left, just the floorpan, front bulkhead and a few sections at either end of the tub. Almost all the bodywork is fashioned from lightweight glassfibre and, while the roof is still metal, it’s made of aluminium to help lower the centre of gravity. The deep-dish wheels are the 917’s 15in centre-lock magnesium alloys, which originally would have been shod with Dunlop slicks. On this bitterly cold day they are instead wearing a set of Avon wets with Dunlop transfers. 
 
The regular 911’s limiting torsion-bar suspension had already been replaced by a coil spring set-up on the 3.0 RSRs, and the Turbo’s chassis was further evolved. Its engineers created a completely bespoke arrangement of box-section aluminium arms and progressive-rate titanium coil springs, anti-roll bars and Bilstein dampers. It saved a massive 27kg (60lb) over that of the regular RSR set-up. 

Porsche 911 RSR Turbo

The result of all these weight-saving measures is impressive. With a full tank of fuel – all 120 litres (26.4 gallons) of it – the RSR Turbo 2.1 weighs in at just 828kg. Less than a Lotus Elise. That’s not simply Porsche’s claim, either, that’s the weight recorded at scrutineering for Le Mans. The long-distance fuel tank isn’t under the bonnet because, although it would help weight distribution, as the tank went from full to empty the front would unload to the tune of 90kg, changing the dynamic balance. Instead the tank sits in the middle of the car next to the driver, leaving a scant 266kg over the front wheels for a very tail-heavy 32:68 split. 
 
Already I’m trying to imagine what that must feel like, and how the RSR will behave when that heavily turbocharged, small-capacity flat-six comes on boost. A colleague speculated that flooring the throttle would be like pulling the pin from a grenade… I’ll find out soon enough, if only from the passenger seat.  
 
‘Seat’ is a generous description. Really it’s a small scoop of glassfibre covered with a swatch of velour, and supported by an aluminium tube at the front and pop-riveted to the bulkhead behind. It looks like it would struggle to cope with a heavy bag of shopping, let alone my weight, but a Group 5 car has to be a two-seater. Technically.
 
‘Be careful, please,’ says Simon. I do my best, lowering myself in gingerly, and – ta-da! – it holds. I am proof that this RSR is a two-seater. It’s a bit cramped, mind; the central fuel tank pushes the rear bulkhead forward and the footwell is foreshortened too, so my knees are up round my ears. I feel like I’m squatting rather than sitting. 

Porsche 911 RSR Turbo
 
Joe fires-up the flat-six, snicks the lever into first and we trundle out onto the circuit, the gravelly-voiced boxer crooning away behind. A squeeze of throttle brings a whoosh of boost and a strengthening of the push. 
 
Joe brakes early for the left that links to the infield section and, as he swings the car in, there’s a sharp crack! The fragile seat gives way and I’m sitting a couple of inches lower, eyes now level with the top of the dashboard. 
 
It means I loll drunkenly into the next corner. To stop myself rolling around and impeding Joe’s gear-shifting I have to shove my left arm down the side of the seat and my right hand high up into the corner of the rollcage. As the lap progresses, Joe coaxes more from the engine, and I’m getting a flavour of the power. When the swell of torque takes hold of what little mass there is, it throws the RSR forward with delicious ease. Shame it is still stumbling with a misfire at around 5500rpm.
 
As period shots show, it’s not a stiffly set-up car so there’s some roll. Occasionally Joe throws in a stab of opposite lock for a reason that I, sitting on something about as stable as a beachball, cannot feel. I can guess, though – it’s just above freezing and when I’d stuck a thumbnail into the tread of those Avon wets the rubber felt like Bakelite. I’m seeing just a glimpse, then, of the RSR’s potential. Oh for a warm track, hot slicks and a proper seat.  
 
After three laps I can brace no longer. Back in the pits I apologise as I extricate myself. ‘It’s been repaired before,’ says Simon, pointing to a discoloured patch on the underside of the seat, the base of which has delaminated like puff pastry. Like many other parts of this car, the seat wasn’t expected to be in service into the next millennium. It’s now been repaired again – good as new. 

Porsche 911 RSR Turbo

It’s agreed that Joe will do two more laps so that we can get some shots of it cornering. Happily, the misfire clears and he stays out for a few more, getting his foot down to 6500rpm and treating us to a louder, more dynamic display. We’re really getting a flavour of what the car sounds like, the wastegate chattering its musical chu-chu-chu-chu-chu on the overrun, the engine note rising and then rising faster as the boost kicks in. And visually it makes more sense when it’s slingshotting away from the apex. 
 
‘It’s clear that they built it to be incredibly driver-friendly,’ says Joe when we catch up in the pits. He’s been lucky enough to drive lots of great Porsche racers – 3.0 RSR, 935, 956, 962 – but, unsurprisingly, this is his first time in an RSR Turbo 2.1. ‘It’s not a lot of effort to drive, as you’d expect of a car that’s designed to be driven for long stints. The clutch has a long travel so, although it’s heavy, it’s not easy to stall, and the gearbox is good. 
 
‘It’s easy to figure out the handling – there’s nothing to catch you out. The steering is light despite not having assistance, and it’s obvious there’s not much weight at the front, but ultimately it seems easy to get into the apex.’ And that engine? ‘Lag is much less than expected but there’s enough to make you think about it. Boost comes in quite low down, so as long as you’ve got it spooled-up early it’s OK. In delivery it’s a lot like a 956. 

Porsche 911 RSR Turbo
 
If you really leaned on it, it would wheelspin – it’s a beast waiting to be unleashed – but with those fat slicks I imagine the advantage it had over the 3.0 RSRs was acceleration out of the corners and top speed. 
 
‘I think it could get quite warm in there. I was cold when we were just trundling around but it heated up once it was going a bit and the fluids really started to flow through the cockpit. Imagine what it would have been like in France in June.’
 
Second at Le Mans was outstanding, but drivers Gijs van Lennep and Herbert Müller could have been standing on the top step. While the sister car, R12, went out after eight hours with an ‘engine-bay fire’ – actually a massive blow-up at max speed caused by crank failure – R13 enjoyed a faultless run and climbed up the order as many of the sports prototypes hit trouble. With six hours to go, R13 was comfortably in second place behind the leading Matra Simca of Henri Pescarolo and Gerard Larrousse when the Matra hit gearbox trouble. 
 
Ironically, it was using a Porsche ’box and the factory sent its two gearbox specialists down to the Matra garage to help out. Some 45 minutes later, the Matra was fixed and heading back out, by which time the Turbo was on the same lap. It was the honourable thing to do but some other companies, seeing an opportunity to win, might not have been so helpful. However, it was then the Porsche’s turn to have gearbox troubles, though that wasn’t enough to prevent it finishing second. 

Porsche 911 RSR Turbo
 
R13 competed three more times that year, van Lennep and Müller scoring another second place in the Watkins Glen 6 Hours, again finishing behind a Matra, followed by seventh at the 1000km at Paul Ricard  and fifth at the Brands Hatch 1000km. It was enough to help Porsche secure third overall in the World Sports Car Championship. 
 
Regulation changes for ’75 led Porsche to create a new racer, but in private hands R13 raced twice in 1977, at the Daytona 24 Hours (DNF – piston failure) and finally at the 3 Hours of Mid-Ohio (26th) – in plain silver. Thankfully that was a fablon wrap and the Martini livery was intact beneath! Of the other RSRs, R12 is still with the factory; R5 and R9 are in private collections.
 
Of course, with the Carrera RSR Turbo, Norbert Singer was just getting started. The crazy-looking, turbocharged 911 prototype paved the way for even more radical and even more successful prototype racers, notably the 935, which in turn laid the groundwork for the Group C cars with which Porsche dominated sports car racing and Le Mans in the ’80s – the 956 and 962.
 
In fact, since the RSR Turbo, all of Porsche’s sports car racers have been turbocharged, right up to the 919. That’s quite some legacy.


 
Thanks to Gooding & Company, which offered the RSR Turbo for sale at Amelia Island, Florida, on 9 March. See www.goodingco.com.


Words: John Barker // Photography: Alex Tapley

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